THE EYES OF ANNULATA IOI 



oval nucleus and tapers into a delicate process which comes into close 

 relation with branches of the two longitudinal nerves of the branchial 

 stem, but a direct continuity of the branches could not be demonstrated 

 with certainty. Transitional hypodermal cells are present around the 

 base of the eye, which show the continuity of the retinal type of cell with 



sp-'J 



sp 



Fig. 65. — Head of Hirudo Medicinalis, showing the Continuity of the Five 

 Pairs of Eyes, with the Rows of Segmental Papillae. 



E l to E 5 : pairs of eyes. s.p. : segmental papillae. 



(From A Textbook of Zoology : Parker and Haswell.) 



on — Vm^*^ 



Fig. 66. — Section of an Eye of a Leech. 

 c. : cuticle. o.n. : optic nerve. 



gl. : glandular cell. p. : pigment. 



hyp. : hypodermis. r.c. : refractile cells. 



n.c. : nerve cells. 



(From Lang's Comparative Anatomy.} 



the hypoderm cells. Andrews examined several other allied species, 

 including Sabella microophthalmia and Hypsicomus, and he mentioned that 

 the compound eyes of Branchiommi Kollikeri are so sensitive to light that 

 the movement of a hand in the air at a distance of a metre from the water 

 containing the animals would cause all the animals to withdraw into their 

 tubes as soon as the shadow fell upon them. 



